Filters and filter materials for the removal of microorganisms and processes for using the same

ABSTRACT

Filters and filter materials for removing microorganisms from a fluid are provided along with processes for using the same. The filters include a housing having an inlet and an outlet and a filter material disposed within the housing, wherein the filter material is formed at least in part from a plurality of filter particles having an activated coating with a lignosulfonate.

FIELD OF THE INVENTION

The present invention relates to the field of filters and filtermaterials for the removal of microorganisms and processes thereof, and,more particularly, to the field of filters and filter materialscomprising particles coated with an activated lignosulfonate.

BACKGROUND OF THE INVENTION

Water may contain many different kinds of contaminants including, forexample, particulates, harmful chemicals, and microbiological organisms,such as bacteria, parasites, protozoa and viruses. In a variety ofcircumstances, these contaminants must be removed before the water canbe used. For example, in many medical applications and in themanufacture of certain electronic components, extremely pure water isrequired. As a more common example, any harmful contaminants must beremoved from water before it is potable, i.e., fit to consume. Despitemodern water purification means, the general population is at risk, andin particular infants and persons with compromised immune systems are atconsiderable risk.

In the U.S. and other developed countries, municipally treated watertypically includes one or more of the following impurities: suspendedsolids, bacteria, parasites, viruses, organic matter, heavy metals, andchlorine. Breakdown and other problems with water treatment systemssometimes lead to incomplete removal of bacteria and viruses. In othercountries, there are deadly consequences associated with exposure tocontaminated water, as some of them have increasing populationdensities, increasingly scarce water resources, and no water treatmentutilities. It is common for sources of drinking water to be in closeproximity to human and animal waste, such that microbiologicalcontamination is a major health concern. As a result of waterbornemicrobiological contamination, an estimated six million people die eachyear, half of which are children under 5 years of age.

In 1987, the U.S. Environmental Protection Agency (EPA) introduced the“Guide Standard and Protocol for Testing Microbiological WaterPurifiers”. The protocol establishes minimum requirements regarding theperformance of drinking water treatment systems that are designed toreduce specific health related contaminants in public or private watersupplies. The requirements are that the effluent from a water supplysource exhibits 99.99% (or equivalently, 4 log) removal of viruses and99.9999% (or equivalently, 6 log) removal of bacteria against achallenge. Under the EPA protocol, in the case of viruses, the influentconcentration should be 1×10⁷ viruses per liter, and in the case ofbacteria, the influent concentration should be 1×10⁸ bacteria per liter.Because of the prevalence of Escherichia coli (E. coli, bacterium) inwater supplies, and the risks associated with its consumption, thismicroorganism is used as the bacterium in the majority of studies.Similarly, the MS-2 bacteriophage (or simply, MS-2 phage) is typicallyused as the representative microorganism for virus removal because itssize and shape (i.e., about 26 nm and icosahedral) are similar to manyviruses. Thus, a filter's ability to remove MS-2 bacteriophagedemonstrates its ability to remove other viruses.

Due to these requirements and a general interest in improving thequality of potable water, there is a continuing desire to provide lowcost filter materials and filters which are capable of removing bacteriaand/or viruses from a fluid. Further, there is a continuing desire toprovide such filter materials in the form of fibers in order to reducethe pressure differential needed to pass a fluid through the filtermaterial.

SUMMARY OF THE INVENTION

Filters and filter materials for removing microorganisms from a fluidare provided along with processes for using the same. In one embodimentof the present invention, the filter includes a housing having an inletand an outlet and a filter material disposed within the housing, whereinthe filter material is formed at least in part from a plurality offilter particles having an activated lignosulfonate coating. A preferredlignosulfonate is ammonium lignosulfonate and exemplary filter particlescan be provided in the form of glass fibers or ceramic fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the invention, it is believed that the presentinvention will be better understood from the following description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a BET nitrogen adsorption isotherm of glass fibers coated withan activated ammonium lignosulfonate in accordance with the presentinvention;

FIG. 2 is a mesopore volume distribution of the glass fibers of FIG. 1;

FIG. 3 is a cross sectional side view of an axial filter made inaccordance with the present invention;

FIG. 4 illustrates the E. coli bath concentration as a function of timefor the glass fibers of FIG. 1; and

FIG. 5 illustrates the MS-2 bath concentration as a function of time forglass fibers coated with an activated zinc lignosulfonate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. Definitions

As used herein, the terms “filters” and “filtration” refer to structuresand mechanisms, respectively, associated with microorganism removal, viaeither adsorption and/or size exclusion.

As used herein, the terms “microorganism”, “microbiological organism”and “pathogen” are used interchangeably. These terms refer to varioustypes of microorganisms that can be characterized as bacteria, viruses,parasites, protozoa, and germs.

As used herein, the phrase “Bacteria Removal Index” (BRI) of filterparticles is defined as:

 BRI=100×[1−(bath concentration of E. coli bacteria at 6 hours)/(controlconcentration of E. coli bacteria at 6 hours)],

wherein “bath concentration of E. coli bacteria at 6 hours” refers tothe concentration of bacteria after 6 hours in a bath that contains amass of filter particles having 1400 cm² of total external surface area,as discussed more fully hereafter. The phrase “control concentration ofE. coli bacteria at 6 hours” refers to the concentration of E. colibacteria after 6 hours in the control bath, and is equal to 1×10⁹ CFU/L.Note that the term “CFU/L” denotes “colony-forming units per liter”,which is a typical term used in E. coli counting. The BRI index ismeasured without application of chemical agents that providebacteriocidal effects. An equivalent way to report the removalcapability of filter particles is with the “Bacteria Log Removal Index”(BLRI), which is defined as:

BLRI=−log[1−(BRI/100)].

The BLRI has units of “log” (where “log” stands for logarithm). Forexample, filter particles that have a BRI equal to 99.99% have a BLRIequal to 4 log. A test procedure for determining BRI and BLRI values isprovided hereafter

As used herein, the phrase “Virus Removal Index” (VRI) for filterparticles is defined as:

VRI=100×[1−(bath concentration of MS-2 phages at 6 hours)/(controlconcentration of MS-2 phages at 6 hours)],

wherein “bath concentration of MS-2 phages at 6 hours” refers to theconcentration of phages after 6 hours in a bath that contains a mass offilter particles having 1400 cm² total external surface area. The phrase“control concentration of MS-2 phages at 6 hours” refers to theconcentration of MS-2 phages after 6 hours in the control bath, and isequal to 1×10⁹ PFU/L. Note that the term “PFU/L” denotes “plaque-formingunits per liter”, which is a typical term used in MS-2 counting. The VRIindex is measured without application of chemical agents that providevirucidal effects. An equivalent way to report the removal capability offilter particles is with the “Viruses Log Removal Index” (VLRI), whichis defined as:

VLRI=−log[100−(VRI/100)].

The VLRI has units of “log” (where “log” is the logarithm). For example,filter particles that have a VRI equal to 99.9% have a VLRI equal to 3log. A test procedure for determining VRI and VLRI values is providedhereafter.

As used herein, the phrase “total external surface area” is intended torefer to the total geometric external surface area of the filterparticles, as discussed more fully hereafter.

As used herein, the term “specific external surface area” is intended torefer to the total external surface area per unit mass of the filterparticles, as discussed more fully hereafter.

As used herein, the term “micropore” is intended to refer to a porehaving a width or diameter less than 2 nm (or equivalently, 20 Å).

As used herein, the term “mesopore” is intended to refer to a porehaving a width or diameter between 2 nm and 50 nm (or equivalently,between 20 Å and 500 Å).

As used herein, the term “macropore” is intended to refer to a porehaving a width or diameter greater than 50 nm (or equivalently, 500 Å).

As used herein, the phrase “pore volume” and its derivatives areintended to refer to the volume as measured by the BET method (ASTM D4820-99 standard), which is well known to those skilled in the art.

As used herein, the phrase “pore size distribution in the mesoporerange” is intended to refer to the distribution of the pore size ascalculated by the Barrett, Joyner, and Halenda (BJH) method, which iswell known to those skilled in the art.

As used herein, the phrase “total pore volume” is intended to refer tothe summation of the volumes of the micropores, mesopores, andmacropores.

As used herein, the term “filter material” is intended to refer to anaggregate of filter particles. Filter particles forming a filtermaterial need not be identical in shape, size, or composition. Forexample, a filter material might comprise granules coated with anactivated lignosulfonate coating and non-coated activated carbon fibers.

As used herein, the phrase “filter particle” is intended to refer to anindividual member or piece which forms at least part of a filtermaterial. For example, a fiber, a granule, a bead, etc. are eachconsidered filter particles herein. The filter particles can be coatedor non-coated.

As used herein, the term “carbonization” and its derivatives areintended to refer to a process in which the non-carbon species in acarbonaceous substance are reduced.

As used herein, the term “activation” and its derivatives are intendedto refer to a process in which a carbonized substance is rendered moreporous.

As used herein, the phrase “total weight of a filter particle” and itsderivatives are intended to refer to the weight of the filter particle,including its coating.

Other terms used herein are defined in the specification wherediscussed.

II. Filter Particles Coated with an Activated Lignosulfonate

Exemplary filter particles coated with an activated lignosulfonate willnow be described. Unexpectedly it has been found thatlignosulfonate-coated filter particles have a large amount of mesoporeand/or macropore volume when carbonized and activated. Although notwishing to be bound by any theory, it is hypothesized that the largenumber of mesopores and/or macropores provide more convenient adsorptionsites for the pathogens, their fimbriae, and surface polymers (e.g.proteins, lipopolysaccharides, carbohydrates and polysaccharides) thatconstitute the outer membranes, capsids and envelopes of the pathogens.This enhanced adsorption might be attributed to the fact that thetypical size of the fimbriae, and surface polymers is similar to that ofthe mesopores and macropores.

The filter particles can be provided in a variety of shapes and sizes.For example, the filter particles can be provided in simple forms suchas granules, fibers, and beads. The filter particles can be provided inthe shape of a sphere, polyhedron, cylinder, as well as othersymmetrical, asymmetrical, and irregular shapes. Further, the filterparticles can also be provided in complex forms such as webs, screens,meshes, non-wovens, and wovens, which may or may not be formed from thesimple forms described above.

Like shape, the size of the filter particle can also vary, and the sizeneed not be uniform among filter particles used in any single filter. Infact, it can be desirable to provide filter particles having differentsizes in a single filter. Generally, the size of the filter particles isbetween about 0.1 μm and about 10 mm, preferably between about 0.2 μmand about 5 mm, more preferably between about 0.4 μm and about 1 mm, andmost preferably between about 1 μm and about 500 μm. For spherical andcylindrical particles (e.g., fibers, beads, etc.), the above-describeddimensions refer to the diameter of the filter particles. For filterparticles having substantially different shapes, the above-describeddimensions refer to the largest dimension (e.g., length, width, orheight).

The filter particles can be formed from a variety of materials, such asmetals, metal alloys, carbon, ceramic or glass. Some typical examples offilter particle materials are: glass fibers, ceramic fibers, carbonfibers, and copper granules. Examples of suitable glass fibers aremilled glass fibers 15.8 μm in diameter and 1.6 mm ({fraction (1/16)}″)in length from Owens Corning, Inc., of Toledo, Ohio, with the followingnotations: 1) 731ED, that contain cationic sizing; 2) 737BD, thatcontain silane sizing, and 3) 739DD, that are unsized. Other examples ofglass fibers are CRATEC® chopped strands from Owens Corning, Inc., andMICROSTRAND® glass microfibers from Johns Manville International, Inc.,of Denver, Colo. Examples of glass fiber webs are the surfacing veilsC64, C33, ECR30A and ECR30S from Owens Corning, Inc, microfiber glassfilter papers 8000130, 8000100, and HD-2233 from Hollingsworth & VoseCompany of East Walpole, Mass., and glass fiber papers grade 151 and 164from A. Ahlstrom Corporation of Helsinki, Finland.

Examples of suitable ceramic fibers are INSULFRAX® and FIBERFRAX® fromUnifrax Corporation of Niagara Falls, N.Y., REFRASIL® from Hitco CarbonComposites of Gardena, Calif., and NICALON® from Nippon Carbon Co., Ltd,of Tokyo, Japan. Examples of ceramic webs are FIBERFRAX® papers, such as550, 882-H, and 972-H, from Unifrax Corporation. Examples of carbonfibers are polyacrylonitrile (PAN) and pitch-based THORNEL fibers fromBP Amoco Polymers, Inc., of Alpharetta, Ga., and FORTAFIL® OPF fromFortafil Fibers, Inc., of Rockwood, Tenn. Copper and brass screens canalso be used.

At least some of the filter particles forming a filter material arecoated with a lignosulfonate to provide the carbon source during thesubsequent steps of carbonization and activation of the filterparticles. As used herein, the term “coated” means either continuous ordiscontinuous, i.e., the coating can completely cover the surface of thefilter particle or covers only a portion so that it forms areas ofcoverage (e.g. “islands”) and areas of no coverage. While the coatingsof the present invention contain lignosulfonate, it is contemplated thatthe coatings can also comprise other substances. For example, thecoatings might contain 90% by weight lignosulfonate and 10% by weightstarch. Other substances can include, but are not limited to, kraftlignin, organosolv lignin, amine lignin, sugar, xylan, cyclodextrin,sodium silicate, chitosan, cellulose acetate, carboxymethyl cellulose,carboxyethyl cellulose, polyvinyl acetate, phenolic resin, polystyrene,polyacrylonitrile, polyethylene terephthalate, pitch, asphalt, acetal,vinyl polymers, acrylic polymers, polyamide epichlorohydrin,polyethylene oxide, polypropylene oxide, polyvinyl methyl ether,polyethylene imine, polyacrylamide, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyvinyl pyridine, and mixtures thereof.

A particularly preferred lignosulfonate is ammonium lignosulfonate (AL).As known in the art, ammonium lignosulfonate is a sulfonate salt, whichis by-product of either the acid sulfite pulping process or thechemi(thermo)mechanical (CTMP) pulping. During the pulping process, thelignin in the wood chips (from either hardwood or softwood) is subjectedto reaction with an aqueous bisulfite salt at elevated temperature andpressure, and is rendered water soluble by depolymerization andsulfonation reactions. Both reactions typically take place in theα-position in the propane side chain of the lignin molecule, and theresulting lignosulfonate molecule contains one sulfonate group per twophenylpropane units, as shown by way of example in formula 1 below.

The typical weight average molecular weight of the ammoniumlignosulfonate is about 30,000, and its number average molecular weightis about 3,000. The resulting lignosulfonate is dissolved in the spentsulfite pulping liquor along with a variety of carbohydrates that areformed by degradation of the hemicellulose components of the wood.

The AL can be provided as a powder, a dispersion, or a solution.Examples of AL solutions are LIGNOSITE® 1740 from Georgia-Pacific West,Inc., of Bellingham, Wash., NORLIG TSFL and NORLIG TSFL-4 fromBorregaard LignoTech, Inc., of Rothschild, Wis., and Weschem AS fromWesco Technologies, Ltd., of San Clemente, Calif. The LIGNOSITE® 1740solution contains 48±2% by weight total solids, more than 60% of whichis AL solids. The Weschem AS dry solids contain more than 57%lignosulfonate and more than 24% reducing sugars by weight.

Other lignosulfonate powders, dispersions or solutions can be used inplace of ammonium lignosulfonate. For example, calcium lignosulfonate(CaLS), zinc lignosulfonate (ZL), ferric lignosulfonate (FL), chromiumlignosulfonate (CrL), magnesium lignosulfonate (MgL), sodiumlignosulfonate (NaLS), copper lignosulfonate (CuLS), and manganeselignosulfonate (MnL) can be used. Examples of zinc lignosulfonate are:in solution form, Weschem Zn from Wesco Technologies, Ltd.; and inpowder form, Zinc KE-MIN® micronutrient lignosulfonate fromGeorgia-Pacific West, Inc., and NORLIG° Zn from Borregaard LignoTech,Inc. Mixtures of the various lignosulfonates can also be used.

The filter particles can be coated with AL using one of many techniquesknown in the art. For example and not by way of limitation, some ways tocoat filter particles are: 1) dispersing the filter particles in the ALsolution; 2) submerging the filter particles into the AL solution, 3)spraying the AL solution onto the filter particles with the use oftypical spraying equipment, such as, but not limited to, triggersprayers, aerosol generators and electrostatic sprayers; and 4) usingtypical coating equipment and practices, such as, but not limited to,roll coating, rod coating and pressure saturation.

Following application of the AL coating, the coated filter particles canbe dried using various methods known to those skilled in the art. Forexample and not by way of limitation, some methods to achieve dryingare: 1) placing the coated filter particles in a convection oven at atemperature of about 100° C.; 2) placing the coated filter particles onair flotation dryers; and 3) infrared (IR) heating. The weight percentof the coating, which is also referred to as “coating add-on”, ismeasured after drying and is calculated as the ratio of the weight ofthe coating to the total weight of the filter particle (i.e., the weightof the filter particle including the coating). The coating add-on isbetween about 0.5% and about 97% of the total weight of the filterparticle and, in an alternate embodiment, is between about 0.6% andabout 90% of the total weight of the filter particle. In anotherembodiment, the coating add-on is between about 1% and about 80%, orbetween about 4% and about 70% of the total weight of the filterparticle.

Carbonization of the coated filter particles is achieved in furnaces.The carbonization conditions include temperature, time and atmosphere,and these conditions can be varied as typically known to those skilledin the art. Exemplary carbonization conditions will now be described. Inthe one process of the present invention, the carbonization temperatureis between about 500° C. and about 1000° C., preferably is between about600° C. and about 900° C., more preferably is between about 630° C. andabout 800° C., and most preferably is between about 680° C. and about750° C. The carbonization time can be between 2 minutes and 5 hours,preferably between about 5 minutes and about 3 hours, more preferablybetween about 10 minutes and about 1.5 hours, and most preferablybetween about 20 minutes and about 40 min. The carbonization atmospherecan include inert gases or nitrogen and their flow rate can be betweenabout 2.5 standard L/h.g (i.e., standard liters per hour and gram ofcarbon in the coating; 0.09 standard ft³/h.g) and about 600 standardL/h.g (21.12 standard ft³/h.g), preferably between about 5 standardL/h.g (0.18 standard ft³/h.g) and about 300 standard L/h.g (10.56standard ft³/h.g), more preferably between about 10 standard L/h.g (0.36standard ft³/h.g) and about 200 standard L/h.g (7.04 standard ft³/h.g),and most preferably between about 50 standard L/h.g (1.76 standardft³/h.g) and about 100 standard L/h.g (3.52 standard ft³/h.g). Theweight percent of carbon in the carbonized coating, which is alsoreferred to as “carbon add-on in the carbonized coating”, is calculatedas the ratio of the weight of the carbon in the carbonized coating tothe total weight of the filter particle (i.e., the weight of the filterparticle including the carbonized coating). The carbon add-on in thecarbonized coating is between about 0.2% and about 95% and, in analternate embodiment, is between about 0.3% and about 85% of the totalweight of the filter particle. In another embodiment, the carbon add-onin the carbonized coating is between about 0.5% and about 70% or betweenabout 1% and about 60% of the total weight of the filter particle.

Activation of the carbonized, coated filter particles can next be donein a furnace. The activation conditions include temperature, time andatmosphere, and these conditions can be varied as typically known tothose skilled in the art. Exemplary activation conditions will now bedescribed. In one process of the present invention, the activationtemperature can be between about 550° C. and about 1300° C., preferablybetween about 600° C. and about 1200° C., more preferably between about650° C. and about 1000° C., and most preferably between about 700° C.and about 900° C. The activation time can be between about 3 minutes andabout 12 hours, preferably between about 5 minutes and about 10 hours,more preferably between about 30 minutes and about 8 hours, and mostpreferably between about 2 hours and about 7 hours. Examples ofactivation atmospheres are (but not limited to) mixtures of oxidants andcarrier gases such as, steam and nitrogen, carbon dioxide and nitrogen,carbon dioxide and steam, etc. The steam flowrate can be between about0.005 mL/min.g (i.e., milliliter per minute and gram of carbon in thecarbonized coating) and about 15 mL/min.g, preferably between about 0.01mL/min.g and about 10 mL/min.g, more preferably between about 0.05mL/min.g and about 5 mL/min.g, and most preferably between about 0.1mL/min.g and about 1 mL/min.g. The weight percent of carbon in theactivated coating, which is also referred to as “carbon add-on in theactivated coating”, is calculated as the ratio of the weight of thecarbon in the activated coating to the total weight of the filterparticle (i.e., the weight of the filter particle including theactivated coating). In one embodiment, the carbon add-on in theactivated coating is less than about 85% or less than about 75%. Inanother embodiment, the carbon add-on in the activated coating isbetween about 0.1% and about 85% and, in an alternate embodiment, isbetween about 0.2% and about 75% of the total weight of the filterparticle. In another embodiment, the carbon add-on in the activatedcoating is between about 0.3% and about 60% or between about 0.5% andabout 45% of the total weight of the filter particle.

The Brunauer, Emmett and Teller (BET) specific surface area and theBarrett, Joyner, and Halenda (BJH) pore size distribution can be used tocharacterize the pore structure of the coated, activated filterparticles. The BET specific surface area is measured according to ASTM D4820-99 standard by multipoint nitrogen adsorption. These methods canalso provide the micropore, mesopore, and macropore volumes. The BJHpore size distribution is measured according to Barrett, Joyner, andHalenda (BJH) method, which is described in J. Amer. Chem. Soc., 73,373-80 (1951) and Gregg and Sing, ADSORPTION, SURFACE AREA, ANDPOROSITY, 2nd edition, Academic Press, New York (1982), the substancesof which are incorporated herein by reference. Both methodologies arewell known in the art.

Preferably, the BET specific surface area of the filter particles coatedwith an activated lignosulfonate is between about 500 m²/g (g refers tothe mass of the carbon in the activated coating) and about 3,000 m²/g,preferably between about 600 m²/g to about 2,800 m²/g, more preferablybetween about 800 m²/g and about 2,500 m²/g, and most preferably betweenabout 1,000 m²/g and about 2,000 m²/g. Referring to FIG. 1, a typicalnitrogen adsorption isotherm, using the BET method, of a glass fibercoated with an activated ammonium lignosulfonate is illustrated.

The total pore volume is measured during the BET nitrogen adsorption andis calculated as the volume of nitrogen adsorbed at a relative pressure,P/P₀ of 0.9814. The total pore volume of filter particles coated with anactivated lignosulfonate is between about 0.4 mL/g (g refers to the massof the carbon in the activated coating) and about 3 mL/g, preferablybetween about 0.5 mL/g and about 2.8 mL/g, more preferably between about0.7 mL/g and about 2.5 mL/g, and most preferably between about 0.8 mL/gand about 2 mL/g. The sum of the mesopore and macropore volumes ismeasured during the BET nitrogen adsorption and calculated as thedifference between the total pore volume and the volume of nitrogenadsorbed at P/P₀ of 0.15. The sum of the mesopore and macropore volumesof filter particles coated with an activated lignosulfonate is betweenabout 0.2 mL/g (g refers to the mass of the carbon in the activatedcoating) and about 2.2 mL/g, preferably between about 0.25 mL/g andabout 2 mL/g, more preferably between about 0.3 mL/g and about 1.7 mL/g,and most preferably between about 0.4 mL/g and about 1.5 mL/g.

In one embodiment, the pore volume is at least about 0.01 mL/g (g refersto the mass of the carbon in the activated coating) for any porediameter between about 4 nm and about 6 nm. In alternate embodiment, thepore volume is between about 0.01 mL/g and about 0.04 mL/g for any porediameter between about 4 nm and about 6 nm. In yet another embodiment,the pore volume is at least about 0.06 ml/g for pore diameters betweenabout 4 nm and about 6 nm or is between about 0.06 ml/g and about 0.15ml/g. In a preferred embodiment, the pore volume is between about 0.07ml/g and about 0.15 ml/g for pore diameters between about 4 nm and about6 nm.

The ratio of the sum of the mesopore and macropore volumes to themicropore volume is between about 0.3 and about 3, preferably betweenabout 0.5 and about 2, more preferably between about 0.65 and about 1.7,and most preferably between about 0.8 and about 1.5. Referring to FIG.2, a typical mesopore volume distribution, as calculated by the BJHmethod, for a glass fiber coated with activated ammonium lignosulfonateis illustrated.

The total external surface area is calculated by multiplying thespecific external surface area by the mass of the coated filterparticles, and is based on the dimensions of the coated filterparticles. For example, the specific external surface area ofmono-dispersed (i.e., with uniform diameter) fibers is calculated as theratio of the area of the fibers (neglecting the 2 cross sectional areasat the ends of the fibers) and the weight of the fibers. Thus, thespecific external surface area of the fibers is equal to: 4/Dρ, where Dis the fiber diameter and ρ is the fiber density. For monodispersedspherical particles, similar calculations yield the specific externalsurface area as equal to: 6/Dρ, where D is the particle diameter and ρis the particle density. For poly-dispersed fibers, spherical orirregular particles, the specific external surface area is calculatedusing the same respective formulae as above after substituting{overscore (D)}_(3,2) for D, where {overscore (D)}_(3,2) is the Sautermean diameter, which is the diameter of a particle whosesurface-to-volume ratio is equal to that of the entire particledistribution. A method, well known in the art, to measure the Sautermean diameter is by laser diffraction, for example using the Malvernequipment (Malvern Instruments Ltd., Malvern, U.K.). The specificexternal surface area of the coated filter particles is between about 10cm²/g (g refers to the mass of the filter particle, including thecoating) and about 100,000 cm²/g, preferably between about 50 cm²/g andabout 50,000 cm²/g, more preferably between about 100 cm²/g and about10,000 cm²/g, and most preferably between about 500 cm²/g and about5,000 cm²/g.

The BRI of the filter particles coated with an activated lignosulfonate,when measured according to the batch test procedure set forth herein, isgreater than about 99%, preferably greater than about 99.9%, morepreferably greater than about 99.99%, and most preferably greater thanabout 99.999%. Equivalently, the BLRI of the filter particles coatedwith an activated lignosulfonate is greater than about 2 log, preferablygreater than about 3 log, more preferably greater than about 4 log, andmost preferably greater than about 5 log. The VRI of filter particlescoated with an activated lignosulfonate, when measured according to thebatch test procedure set forth herein, is greater than about 90%,preferably greater than about 95%, more preferably greater than about99%, and most preferably greater than about 99.9%. Equivalently, theVLRI of the filter particles coated with an activated lignosulfonate isgreater than about 1 log, preferably greater than about 1.3 log, morepreferably greater than about 2 log, and most preferably greater thanabout 3 log.

In one preferred embodiment of the present invention, the filterparticles comprise glass fibers coated with activated ammoniumlignosulfonate. These fibers have a BET specific surface area betweenabout 1,000 m²/g and about 2,000 m²/g, total pore volume between about0.8 mL/g and about 2 mL/g, and sum of the mesopore and macropore volumesbetween about 0.4 mL/g and about 1.5 mL/g.

In another preferred embodiment of the present invention, the filterparticles comprise ceramic fibers coated with activated ammoniumlignosulfonate. These fibers have a BET specific surface area betweenabout 1,000 m²/g and about 2,000 m²/g, total pore volume between about0.8 mL/g and about 2 mL/g, and sum of the mesopore and macropore volumesbetween about 0.4 mL/g and about 1.5 mL/g.

In yet another preferred embodiment of the present invention, the filterparticles comprise glass fibers coated with activated zinclignosulfonate. These fibers have a BET specific surface area betweenabout 1,000 m²/g and about 2,000 m²/g, total pore volume between about0.8 mL/g and about 2 mL/g, and sum of the mesopore and macropore volumesbetween about 0.4 mL/g and about 1.5 mL/g.

The following non-limiting examples are intended to illustratemanufacture of filter materials of the present invention.

EXAMPLE 1 Glass Fibers Coated with Activated Ammonium Lignosulfonate

250 mL of LIGNOSITE® 1740 ammonium lignosulfonate (AL) solution fromGeorgia-Pacific West Inc., of Bellingham, Wash., is diluted with 250 mLof water, and then mixed with 150 g of milled glass fibers 737BD{fraction (1/16)}″ (1.6 mm) in length manufactured by Owens Corning,Inc., of Toledo, Ohio, in an 800 mL beaker for 5 min with gentlestirring. Excess ammonium lignosulfonate solution is removed from thecoated glass fibers using a standard Buchner funnel. The ammoniumlignosulfonate coated glass fibers are then dried at 65° C. for 12 h.

For the carbonization step, the coated glass fibers are placed inside aLindberg/Blue M horizontal tube furnace Model # HTF55667C manufacturedby SPX Corp., of Muskegon, Mich. The furnace temperature is ramped to700° C. with a rate of 7° C./min, and the carbonization goes on for 30min in a flowing nitrogen atmosphere with a nitrogen volumetric flowrateof 30 standard ft³/h (850 L/h).

The carbonized coated glass fibers are then activated in the same tubefurnace at 750° C. for 6 h in a flowing nitrogen/steam atmosphere. Thenitrogen flowrate is 15 standard ft³/h (425 L/h), and the water flowrateis 20 mL/min.

EXAMPLE 2 Glass Fibers Coated with Activated Zinc Lignosulfonate

50 g of powder Zinc KE-MIN® micronutrient lignosulfonate (ZL) fromGeorgia-Pacific West Inc., of Bellingham, Wash., are dissolved in 200 mLof water. The ZL solution is then mixed with 130 g of milled glassfibers 737BD {fraction (1/16)}″ (1.6 mm) in length manufactured by OwensCorning, Inc., of Toledo, Ohio, in an 800 mL beaker for 5 min withgentle stirring. Excess zinc lignosulfonate solution is removed from thecoated glass fibers using a standard Buchner funnel. The zinclignosulfonate coated glass fibers are then dried at 65° C. for 12 h.

For the carbonization step, the coated glass fibers are placed inside aLindberg/Blue M horizontal tube furnace Model # HTF55667C (SPX Corp.;Muskegon, Mich.). The furnace temperature is ramped to 700° C. with arate of 7° C./min, and the carbonization goes on for 30 min in a flowingnitrogen atmosphere with a nitrogen volumetric flowrate of 30 standardft³/h (850 L/h).

The carbonized coated glass fibers are then activated in the same tubefurnace at 750° C. for 6 h in a flowing nitrogen/steam atmosphere. Thenitrogen flowrate is 15 standard ft³/h (425 L/h), and the water flowrateis 20 mL/min.

III. Filters of the Present Invention

Referring to FIG. 3, an exemplary filter made in accordance with thepresent invention will now be described. The filter 20 comprises ahousing 22 in the form of a cylinder having an inlet 24 and an outlet26. The housing 22 can be provided in a variety of forms depending uponthe intended use of the filter. For example, the filter can be an axialflow filter, wherein the inlet and outlet are disposed so that theliquid flows along the axis of the housing. Alternatively, the filtercan be a radial flow filter wherein the inlet and outlet are arranged sothat the fluid (e.g., either a liquid, gas, or mixture thereof) flowsalong a radial of the housing. Still further, the filter can includeboth axial and radial flows. While the filters of the present inventionare particularly suited for use with water, it will be appreciated thatother fluids (e.g., air, gas, and mixtures of air and liquids) can beused. The size, shape, spacing, alignment, and positioning of the inlet24 and outlet 26 can be selected, as known in the art, to accommodatethe flow rate and intended use of the filter 20. The filter 20 alsocomprises a filter material 28, wherein the filter material 28 includesone or more filter particles (e.g., fibers, granules, etc.). One or moreof the filter particles can be coated with an activated lignosulfonateand possess the characteristics previously discussed. The filtermaterial can also comprise uncoated particles and particles formed fromother materials, such as carbon powders, activated carbon granules,activated carbon fibers, zeolites, and mixtures thereof.

IV. Test Procedures

The following test procedures are used to calculate the BRI/BLRI,values, the VRI/VLRI values, and the BET values discussed herein. Whilemeasurement of the BRI/BLRI and VRI/VLRI values is with respect to anaqueous medium, this is not intended to limit the ultimate use of filtermaterials of the present invention, but rather the filter materials canultimately be used with other fluids as previously discussed even thoughthe BRI/BLRI and VRI/VLRI values are calculated with respect to anaqueous medium. Further, the filter materials chosen below to illustrateuse of the test procedures are not intended to limit the scope of themanufacture and/or composition of the filter materials of the presentinvention or to limit which filter materials of the present inventioncan be evaluated using the BRI/BLRI and VRI/VLRI test procedures.

Carbon Add-on and BET Test Procedures

The carbon add-on in the activated coating of the filter material can bemeasured thermo gravimetrically using a Hi-Res Modulated TGA 2950manufactured by TA Instruments, Inc. of New Castle, Del. The TGA finaltemperature is set to 650° C., and the ramp is set to 50° C./min. Thecarbon add-on in the activated coating of the filter materials ofExamples 1 and 2 are about 1.7% and about 0.9%, respectively. The BETspecific surface area and pore volume distribution are measured usingthe nitrogen adsorption technique at 77K with a Coulter SA3100 SeriesSurface Area and Pore Size Analyzer manufactured by Coulter Corp., ofMiami, Fla. For the filter material of Example 1, the BET area is 1,472m²/g, micropore volume is 0.61 mL/g, and the sum of the mesopore andmacropore volumes is 0.86 mL/g. Typical BET nitrogen isotherm and thepore volume distribution for the filter material of Example 1 areillustrated in FIGS. 1 and 2, respectively. For the filter material ofExample 2, the BET area is 1,631 m²/g, micropore volume is 0.72 mL/g,and the sum of the mesopore and macropore volumes is 0.67 mL/g. As willbe appreciated, other instrumentation can be substituted for the TGA andBET measurements as is known in the art.

BRI/BLRI Test Procedure

A PB-900™ Programmable JarTester manufactured by Phipps & Bird, Inc., ofRichmomd, Va., with 2 beakers is used. The diameter of the beakers is11.4 cm (4.5″) and the height is 15.3 cm (6″). Each beaker contains 500mL of contaminated water and a stirrer that is rotated at 60 rpm. Thestirrers are stainless steel paddles 7.6 cm (3″) in length, 2.54 cm (1″)in height, and 0.24 cm ({fraction (3/32)}″) in thickness. The stirrersare placed 0.5 cm ({fraction (3/16)}″) from the bottom of the beakers.The first beaker contains no filter material and is used as a control,and the second beaker contains a sufficient quantity of the filtermaterial so that there is a total external geometric surface area of1400 cm² in the second beaker. For example, if the filter material ofExample 1 is tested, 1.5 g of the AL coated glass fiber particles areplaced in the second beaker. This amount is calculated based on thedensity of the fibers (i.e., 2.6 g/cm³) and their diameter (i.e., 15.8μm), so that the total external geometric surface area is about 1400cm². Duplicate samples of water, 5 mL in volume each, are collected fromeach beaker for assay at the following times after insertion of the ALcoated glass fiber filter particles in the second beaker: 0, 2, 4 and 6hours. Other equipment can be substituted as known in the art.

The E. coli bacteria used are the ATCC # 25922 (American Type CultureCollection, Rockville, Md.). The target E. coli concentration in thecontrol beaker is set to be between 2.0×10⁹ CFU/L and 1.0×10⁹ CFU/L. TheE. coli assay can be conducted using the membrane filter techniqueaccording to method #9222 of the 20^(th) edition of the “StandardMethods for the Examination of Water and Wastewater” published by theAmerican Public Health Association (APHA), Washington, D.C. The limit ofdetection (LOD) is 1×10³ CFU/L. Other assays for determining the E. coliconcentration can be substituted as known in the art.

Exemplary BRI/BLRI results for the filter material of Example 1 areshown in FIG. 4. The E. coli concentration in the control beaker at 6hours is 1.1×10⁹ CFU/L, and that in the second beaker containing the ALcoated glass fiber filter particles is less than the LOD. The BRI isthen calculated as greater than 99.9999%, and the BLRI is calculated asgreater than 6 log.

VRI/VLRI Test Procedure

The testing equipment and the procedure are the same as in BRI/BLRIprocedure. The first beaker contains no filter material and is used ascontrol, and the second beaker contains a sufficient quantity of thefilter material so that there is a total external geometric surface areaof 1400 cm² in the second beaker. For example, if the filter material isthat of Example 2, 1.5 g of the zinc coated glass fiber particles areplaced in the second beaker. This amount is calculated based on thedensity of the fibers (i.e., 2.6 g/cm³) and their diameter (i.e., 15.8μm), so that the total external geometric surface area is about 1400cm².

The MS-2 bacteriophages used are the ATCC # 15597B from the AmericanType Culture Collection of Rockville, Md. The target MS-2 concentrationin the control beaker is set to be between 2.0×10⁹ PFU/L and 1.10×10⁹PFU/L. The MS-2 can be assayed according to the procedure by C. J.Hurst, Appl. Environ. Microbiol., 60(9), 3462(1994). Other assays knownin the art can be substituted. The limit of detection (LOD) is 1×10³PFU/L.

Exemplary VRI/VLRI results for the filter material of Example 2 areshown in FIG. 5. The MS-2 concentration in the control beaker at 6 hoursis 1.1×10⁹ PFU/L, and in the second beaker containing the ZL coatedglass fiber particles is 8.1×10⁶ PFU/L. The VRI is then calculated asequal to 99.3%, and the VLRI is calculated as equal to 2.13 log.

The embodiments described herein were chosen and described to providethe best illustration of the principles of the invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variations are within the scope of the invention asdetermined by the appended claims when interpreted in accordance withthe breadth to which they are fairly, legally and equitably entitled.

What is claimed is:
 1. A filter comprising: a) a housing having an inletand an outlet; and b) a filter material for removing microorganisms fromwater, said filter material disposed within said housing, said filtermaterial formed at least in part from a plurality of filter particlescomprising a carbonized and activated lignosulfonate coating, whereinthe sum of mesopore and macropore volumes of one or more of saidcarbonized and activated ligosulfonate coated filter particles isbetween about 0.2 mL/g and about 2.2 mL/g.
 2. The filter of claim 1,wherein said lignosulfonate is selected from the group consisting ofammonium lignosulfonate, zinc lignosulfonate, calcium lignosulfonate,ferric lignosulfonate, magnesium lignosulfonate, chromiumlignosulfonate, manganese lignosulfonate, sodium lignosulfonate, copperlignosulfonate, and mixtures thereof.
 3. The filter of claim 1, whereinsaid filter material is formed at least in part from one or acombination of glass fibers, screens, ceramic fibers, and non-wovens,comprising a carbonized and activated lignosulfonate coating.
 4. Thefiler of claim 1, wherein the BET surface area of one or more of saidcarbonized and activated lignosulfonate coated filter particles isbetween about 500 m²/g and about 3000 m²/g.
 5. The filter of claim 1,wherein the carbon add-on in said carbonized and activatedlignosulfonate coating is between about 0.1% and about 85%.
 6. Thefilter of claim 1, wherein the carbon add-on in said carbonized andactivated lignosulfonate coating is between about 0.5% and about 45%. 7.The filer of claim 1, wherein the ratio of the sum of the mesopore andmacropore volumes to the micropore volume of one or more of saidcarbonized and activated lignosulfonate coated filter particles isbetween about 0.3 and about
 3. 8. A filter comprising: a) a housinghaving an inlet and an outlet; and b) a filter material for removingmicroorganisms from water, said filter material disposed within saidhousing, said filter material formed at least in part from a pluratlityof filter particles comprising a carbonized and activated lignosulfonatecoating, wherein the carbon add-on in said carbonized and activatedlignosulfonate coating is less than about 85% and wherein the BRI ofsaid filter particles is greater than 99%, and wherein the sum ofmesopore and macropore volumes of one or more of said carbonized andactivated lignosulfonate coated filter particles is between about 0.2mL/g and about 2.2 mL/g.
 9. The filter of claim 8, wherein saidplurality of filter particles have a BRI greater that about 99.9%. 10.The filter of claim 8, wherein said plurality of filter particles have aBRI greater that about 99.99%.
 11. The filter of claim 8, wherein saidplurality of filter particles have a BRI greater than about 99.999%. 12.The filter of claim 8, wherein said plurality of filter particles have aVRI greater than about 90%.
 13. The filter of claim 8, wherein saidplurality of filter particles have a VRI greater than about 95%.
 14. Thefilter of claim 8, wherein said plurality of filter particles have a VRIgreater than about 99%.
 15. The filter of claim 8, wherein saidplurality of filter particles have a VRI greater than about 99.9%. 16.The filter of claim 8, wherein said filter material is formed at leastin part from one or a combination of glass fibers, screens, ceramicfibers, and wovens, comprising a carbonized and activated lignosulfonatecoating.
 17. The filter of claim 8, wherein the carbon add-on in saidcarbonized and activated lignosulfonate coating is between about 0.1%and about 75%.
 18. The filter of claim 8, wherein the carbon add-on insaid carbonized and activated lignosulfonate coating is between about0.5% and about 45%.
 19. The filter of claim 8, wherein saidlignosulfonate is selected from the group consisting of ammoniumlignosulfonate, zince lignosulfonate, calcium lignosulfonate, ferriclignosulfonate, magnesium lignosulfonate, chromium lignosulfonate,manganese lignosulfonate, sodium lignosulfonate, copper lignosulfonate,and mixtures thereof.
 20. The filter of claim 8, wherein the BET surfacearea of one or more of said carbonized and activated lignosulfonatecoated filter particles is between about 500 m²/g and about 3000 m²/g.21. The filter of claim 8, wherein the ratio of the sum of the mesoporeand macropore volumes to the micropore volume of one or more of saidcarbonized and activated lignosulfonate coated filter particles isbetween about 0.3 and about
 3. 22. A filter comprising: a) a housinghaving an inlet and an outlet; and b) a filter material for removingmicroorganisms from a fluid, said filter material disposed within saidhousing, said filter material formed at least in part from a pluralityof filter particles comprising a carbonized and activated lignosulfonatecoating, wherein the carbon add-on in said carbonized and activatedlignosulfonate coating is less than 85%, and wherein the BRI of saidfilter particles is greater than 99.9%, and the VRI of said filterparticles is greater than about 95%, and wherein the sum of mesopore andmacropore volumes of one or more of said carbonized and activatedlignosulfonate coated filter particles is between about 0.2 mL/g andabout 2.2 mL/g.
 23. The filter of claim 22, wherein said lignosulfonateis selected from the group consisting of ammonium lignosulfonate, zinclignosulfonate, calcium lignosulfonate, ferric lignosulfonate, magnesiumlignosulfonate, chromium lignosulfonate, manganese lignosulfonate,sodium lignosulfonate, copper lignosulfonate, and mixtures thereof. 24.The filter of claim 22, wherein said filter material is formed at leastin part from one or a combination of glass fibers, screens, ceramicfibers, and non-wovens, comprising a carbonized and activatedlignosulfonate coating.
 25. The filter of claim 22, wherein the BETsurface area of one or more of said carbonized and activatedlignosulfonate coated filter particles is between about 500 m²/g andabout 3000 m²/g.
 26. The filter of claim 22, wherein the ratio of thesum of the mesopore and macropore volumes to the micropore volume of oneor more of said carbonized and activated lignosulfonate coated filterparticles is between about 0.3 and about 3.